open source

Open source software is software distributed under an open source license. Such a license specifically allows anyone to copy, modify, extend and redistribute the source code without paying royalties or fees to the original authors. Open Source Stack Exchange is a dedicated place for these questions as well.

When you think of open source software, you might think of a few specific projects depending on your area of interest. If you work on web applications, the term "open source" might conjure up visions of Apache or Node.js; if you're into big data, then perhaps Hadoop comes to mind; if you care a lot about security, you might think of OpenSSL; if you're a front-end developer, then maybe jQuery and React pop into your head.